How much esophageal pressure-guided end-expiratory transpulmonary pressure is sufficient to maintain lung recruitment in lavage-induced lung injury?

Abstract

Because of limitations of the esophageal balloon technique, the value of using esophageal pressure (Pes)-guided end-expiratory transpulmonary pressure (PL-exp) to maintain lung recruitment in adult respiratory distress syndrome is controversial. This study aimed to investigate whether tailoring PL-exp to greater than 0 was enough to maintain lung recruitment. Ten pigs with severe lavage-induced lung injury were mechanically ventilated in a decremental positive end-expiratory pressure (PEEP) trial that was reduced from 20 to 6 cm H2O after full-lung recruitment. Respiratory mechanics, blood gases, hemodynamic data, and whole-lung computed tomography scans were recorded at each PEEP level. Open-lung PEEP (OL-PEEP) was determined by computed tomography, while Pes-guided PEEP (Pes-PEEP) was to maintain PL-exp greater than 0. OL-PEEP was higher than Pes-PEEP, which induced a higher PL-exp at OL-PEEP than at Pes-PEEP (4.6 [1.6] cm H2O vs. 1.2 [0.6] cm H2O, p < 0.001). Compared with OL-PEEP, the nonaerated lung region was significantly increased at Pes-PEEP. Superimposed pressure (SP) of the lung tissue between the esophageal plane and the dorsal level was higher at Pes-PEEP than at OL-PEEP, whereas PL-exp at the dorsal level was lower at Pes-PEEP than at OL-PEEP (-1.5 [0.7] cm H2O vs. 2.5 [1.5] cm H2O, p < 0.001). The SP correlated with PL-exp at the dorsal level and the nonaerated lung region. In this surfactant-depleted model, maintaining PL-exp just greater than 0 using Pes was unable to maintain lung recruitment; this was partly caused by a lack of compensation for the increased SP between the esophageal plane and the dorsal level.